In Wiman, U., Automotive Engineering 16 (2008):10, p. 34, 36, “Shear plate reduces diesel engine noise”, there is disclosed a vibration damping plate for mounting between the engine block and the oil pan below the crankshaft in an internal-combustion engine. The damping plate, referred to as a “shear plate”, consists of a sandwich laminate including a middle rubber layer vulcanized together with two steel layers. The shear plate has milled grooves in the steel layers held together by the middle rubber layer. When the upper steel layer is fastened to one side of the engine block, and the lower layer is fastened to the other, it permits shearing, and thus, damping, in the middle layer.
An improvement of this approach is described in our co-pending international application entitled “Vibration damped article”, where the damping plate is mounted to opposed sidewalls of the oil pan rather than between the engine block and the oil pan, and where each metal layer has a cut or groove through the metal layer, and preferably also through at least part of the middle elastomer layer, thereby removing the direct vibration transmission paths through the metal layers from the metal/elastomer layer portion attached to one side wall of the oil pan to that attached to the other sidewall.
Milling such cuts or grooves in the damping plate steel layers is, however, a rather complicated and costly procedure, and a more convenient and simpler method would be desired. It is the object of the present invention to provide such a method.